Radio repeating system



Sept. 15, 1925. v 1,553,454

DE LOSS K. MARTIN RADIO REPEATING SYSTEM in ii? 2 IN VEN TOR ATTORNEY Sept. 15, 1925. I 1,553,454

DE LOSS K. MARTIN RADIO REPEATING SYSTEM INVENTOR ATTORNEY Patented Sept. 15, 1925.

UNITED sra'rl-zs 1,553,454 PATENT OFFICE, 3

nE Loss 1:. MARTIN, or ORANGE, NEW JERSEY, assrenon'ro AMERICAN TELEPHONE- AND TELEGRAPH-COMPANY, A CORPORATION on NEW YORK.

RADIOBREPEATING sys'rinvr.

Application filed January 18, 1923. Serial No. 613,460.

To all whom it may concern:

residing at Orange, in the county of Essex and State of New Jersey, have invented certain Improvements in Radio Repeating Systems, of which the following is a specification.

Thisinventionrelates to radio signaling systems and particularly to a system employing one or more repeater stations between the terminal stations of such a system, which repeater stations are characterized by a change of frequency between the input and output sides thereof and so arranged as to require the minimum number of frequencies consistent with the avoidance of interference at the repeater itself or between adjacent repeaters. In the operation of a long distance radio system having one or more repeaters. between the terminal stationsthereof, it has been necessary to change the received frequencies of each transmission channel at each repeater in order to prevent currents transmitted from the said repeater from enteringthereceivingcircuits of the same repeater, or the receiving circuits for other channels at a distant repeater, thereby preventing singing or cross-modulation between such channels; 'For a system without repeaters, two frequencies are normally -re quired for each channel, one, for transmitting in one direction and another for transmitting in the other direction. If, for the purpose of illustration we consider a system having two terminals and a single repeater therebetween and if we transmit from one terminal a frequency f, and from the other terminal a frequency f,, we can avoid interference at the repeater by changing the frequency f to before radiating it therefrom to the distant terminal to which the signal is intended to go and, similarly, we can change the frequency 7,

r at the repeater station to the frequency 7,

before radiating it therefrom. While interference would thereby beavoided, both at the repeater station and also at the termi nal stations, it is obvious that such a system requires four-frequencies inorder to effect two-way transmission between terminal stations. It is obvious that the frequency range required for such a radio repeater system will increase directlyvwith the number of channels and repeaters in-the system.

, If two or three repeaters are included in Be it known that I, DE Loss K. MARTIN,'..

such a system, the number of frequencies required for the system will, in general, be increased two, per channel per repeater The large demand made upon the available frequencies by such a system greatly reduces the utilityof radio repeaters. How- 7 ever, by the use of directive means of transmission and reception, and means for spacing and controlling the frequencies, it is possible to operate a repeater system with only two frequencies per channel.

It is the object of this invention to effect transmission by a radio system employing one or more repeaters, ln'whlch system the number of frequencies per channel of transmission is, in general, limited to two per channel of transmission, regardless of the number of repeatersemployed.

Other objects of this invention will be apparent from the following description when read in connection with the attached drawing, of which Figure 1 shows graphically the frequency distribution in a repeater system in which for each two-way transmission channel the terminal stations transmit on different frequencies; Fig. 2 shows a circuit arrangement at arepeater station in which the principle of operation of the sys tem shown in Fig. 1 maybe carried out; Fig. 2 shows the directional characteristics of the antenna systems shown in Fig. 2; Fig. 3 shows graphically-the frequency distribution in a system in which transmission at both stations isat the same frequency and similarly reception at both stations is upon the same frequency; Fig. 4 shows the circuit arrangement at a repeater station for carrying out the principle of operation of the systemshown in Fig. 3; and Figures 5 and 5 are directional characteristics explanatory of the system.

It is desired touclearly 'set forth at this i point that 'whileireferen'ce may be made throughout the description of these various embodiments of my invention of the use of 3 a single frequency as, for example, 7, or i as representing the transmitted or received frequencies constituting a transmission f ignation' of these channels by single frequenoy waves is for the purpose of renderchannehitis to be understood that the des- 1105 V sion or reception upon a single frequency. The transmitted and the received waves of each channel may, of course, be a side band of frequencies produced by the modulation of a carrier frequency by the frequencies within the voice ra-nge,-such as. is done in radio telephony, or by the modulation of a carrier frequency by telegraph frequencies, such as is employed in radio telegraphy.

In a system, such as is represented graphically by Fig. 1, a frequency f produced by the modulation of a carrier frequency f,, some definite frequency or frequencies that may be designated 8 is transmitted from station A in the direction of station B in order to transmit a signal therebetween. In like manner, transmission from station B to station A is effected by a frequency f which may be produced by the modulation of a carrier frequency f, by a signaling frequency which may be designated 8, that is to say, the frequency f, may be considered as made up of f +s and the frequency f as being made up of f s. it will be seen that the frequency f transmitted from station A, will, upon its receipt at the radio repeater station BB be translated to frequency f and transmitted therefrom to the repeater BB wherein it will again be-translated to the frequency f and transmitted to the receiving station B. In similar manner, frequency f will be transmitted from the station B and upon its receipt at the repeater R11 will be translated to the frequency f and transmitted to repeater EH where in it will again be translated to frequency f and transmitted to station A.

The manner in which this is carried out will be clearly understood from a consideration of the circuit arrangement shown in Fig. 2, which is illustrative of a desired form of arrangement for effecting this result. In Fig. 2, R R R R; and R represent a plurality of receiving antennae which are coupled by means of the transformers 1, 2, 3, 4 and 5 to a plurality of parallel circuits. Thus, for example, the antenna R is coupled by means ofa transformer 1 with the parallel circuits 6 and 7, each of which has connected thereto a phase shifting de vice designated PS and PS respectively. The receiving antenna R is coupled by means of the, transformer 2 with the parallel circuits 8 and 9, with which are connected the phase shiftingdevices PS and PS respectively and similarly the receiving antennae R R -and R are connected by the transformer 23, 4 and 5respectively with pairs ofparallelcircuits 10 and 11, 12 and 13, 14 and 15, with-which circuits the phase shifting devices PS5 and PS PS and PS PS, and PS, are respectively connected. WVhat may be termed the output side of each odd numbered phaseshifting'device, PS

From Fig. 1

PS etc., is connected with a common trunk circuit L and similarly the output side of each even numbered phase shifting device is connected with a common trunk, circuit L The circuit L is connected through a translating circuit with another common trunk circuit L from which a plurality of branch circuits lead to the transmitting antennae T T T T and T Each branch circuit of the trunk circuit L contains a phase shifting device designated PS PS P8 PS and PS Furthermore, there is associated with each transmitting antenna a power amplifier designated A A A The translating circuit connecting the common trunk circuit L with the common trunk circuit L contains a band filter F a demodulator M,, a low pass filter F an amplifier A a modulator M a band filter F and an amplifier A The filters are preferably of the type shown in thepatent to Campbell, No. 1,227,113, dated May 22, 1917. The modulating and demodulating devices are preferably of the well known vacuum tube type and desirably of a form in which the fundamental carrier frequency is suppressed therein and not transmitted through the output side of such device. The amplifiers are also preferably of the vacuumtube type and may be, of any number of stages necessary for desirable operation.

The common trunk circuit L is likewise connected through a translating circuit to a common trunk L which has a plurality of branch circuits extending to the transmitting antennze T T etc., the said branches containing a plurality of phase shifting devices PS PS etc. The latter translating circuit is similar to the first mentioned translating circuit and contains a band filter F a demodulator M a low pass filter F an amplifier A a modulator M a band filter F and an amplifier A4. A source of high frequency oscillations O is arranged symmetrically with respect to the translating circuits and is connected with the demodulators M and M and the modulators M and M This oscillator has connected therewith an antenna R adapted to receive oscillations from the terminal stations thereby controlling the frequency of the oscillations set up in O which in turn controls the de modulating and modulating processes.

control device C is inserted between the antenna R and the oscillator O for control purposes. 7

The recelvlng antennae and the transmitting antennae constitute two arrays, the purpose of which is to control the directivity ofthe system, and while only five antennae have been shown in connection with each array, 1t is to be understood that the number In the system shown RR would preferably be of the type shown in Fig. 2. The stations A and 13 might be of any well known type embodying either a single antenna structure or a multipleantenna structure in the form of an antenna array. a

Let it be assumed that a wave of the frequency f, is transmitted from station A, which may be called'the west station, and impinges upon the receiving antennae R to R inclusive-so as to set up oscillations therein. By the proper adjustment of the phase shifting devices PS PS PS PS and PS,, the system, which includes the common trunk L may be made efficient for reception from the west. In other words, the receiving structure which includes the branch circuits 6, 8, and 10, etc., and the odd numbered phase shifting devices connected by branches to the common trunk circuit L can be made highly selective from the west, that is to say, its directional characteristic would be as represented by a of Fig. 2*. It is true that some of the energy received from the West would also pass into the branch circuits 7, 9, 11, etc., but since, as will later be shown, the phase shifting devices PS PS etc., arearranged to insure the proper phasing of the currents in the line L only for waves impinging upon the antennae R R etc., from the east, substantially none of the oscillations from the west will pass into the line L vbecause'the direction from which they approach the antenna array is not that for whichqthe even numbered phase shifters are adjusted. The high frequency current set up in the common trunk circuit L by the wavefrom the west, will pass through the filter F which is adapted to pass the frequency f and will be impressed upon the demodulator M Simultaneouswith the impression of the frequency f, on the demodulator, there will also be impressed thereon the frequency f,, set up by the oscillator O, and the product of demodulation will be impressed upon the filter F Since, as has been stated, the frequency 7, may be considered as equal to f-l-s, the result of homodyning the frequency f, with f, is the signal frequency 8. The signal frequency transmitted by the filter F and amplified by the amplifier A,, will be impressed upon the modulator M simultaneous with the impression thereon, of oscillations of the frequency f,. The results of modulation, namely, the side bands f,{'s and fl-s, will be impressed upon the filter F which is designed to pass'only one of the side bands, viz, f s, which, as heretofore stated, equals f This frequency, f when amplified by A is impressed upon the common trunk circult L which in turn impresses it upon the branch circuits containing the odd numbered phase shifting devices; These devices are so adj usted that the oscillations will be applied to the power amplifiers and thereby to the trans -mitting antennae T T etc., in such phase radiation from v the transmitting antennae will be toward the" relation that the direction of east, 'as' shown by b of Fig. 2. It should be noted that by the proper adjustment of the odd numbered phase shifting devices connected between the receiving antennae and the line L the repeater system was from west to east. So to revert to Fig. 1, the 1 oscillations of frequency f,, which constitute one side band of vfrequency f trans- 'mitted from station A to translated to a frequency f which is the op fposite side band of the carrier frequency f,

repeater. RR are and is transmitted mainly in the direction of the repeater BB V g At BB this frequency f, would be retranslated' to the frequency f, and transmitted to station B. in the same manner in which reception, translation and transmis-"- sion has been described in; connection with repeater RR The frequency f transmit-1 ted from station B, will'be translated at repeateriRR to the frequency f, and will-be impressed upon the receiving antennaofrepeaterRR Since we have described the method of translating the oscillations transmitted from west to east, through this re-t I "peater, it isdesirable in order to complete thedescription to describe the translation of the east to west signals. The oscillations impressed upon the receiving antenna array from the east will'be impressed upon both the even numbered as well as'the odd numbered branch circuits connected with the individualantennae constituting the array.

Since the odd numbered phase shifting devices are not adjusted'to properly phas'ethe resulting currents when the wave arrives from the east, substantially no current will result in the line L On the other hand,

since the even numbered phase shifting devices are adjusted to properly phase the resultant currents, due to oscilla tions arriving from the east, the resultant 1 current will be set up in the common trunk L and will be impressed upon, the

filter F which is adapted to pass the frequency f This frequency will be 'homodyned with the frequency A from. the os'cil} lator O and current of the resultant fre quency s will, pass throughthe filter F; and

be amplified at A andin turn be impressed upon the'modulator M together with the carrier frequency f The results of modulation will be impressed upon the filter F f whichis adapted to pass current of the lower side band, that is to say, F and this current, when amplified by A,, will be impressed upon the common trunlrL which in turn impresses it upon the various branch circuits containing even numbered phase shifting devices. These devices are so adjusted that the wave resulting from the oscillations set up in the individual antennae will be transmitted toward the west, as represented by a of Fig. 2. I

Itwill be see-n from the foregoing description that only two frequencies are required in this radio repeating system, even though two repeater points exist between the terminals thereof. The avoidance of interference is partly effected by the use of directive antenna. arrays or equivalent means for reception and transmission. Interference is furthermore prevented by rc ceiving from both directions at substantially the same frequency and transmit ting in both directions at the same frequency the latter frequency being difierent and widely separated from the first mentioned frequency. This separation of the transmitted and the received frequencies'tends to prevent singing between the transmitting and the receiving antennae of the repeater station, which might occur if a transmitted frequency were substantially thesame as a receiving frequency, even though the transmitted frequency were mainly directed in an opposite direction to that from which the receiving antennae were intended to receive.

Figure 3 shows a system in which transmission.fro1n station A and station 13 occurs at a frequency f, and reception at both stations'occurs atthe frequency f,, both of which frequencies may be presumed to be side bands of a carrier frequency f The arrangement for effecting reception, translation and transmission at each of the repeater points RR BB and R11 is shown in Fig. At. This arrangement comprises two. loop antenna: LA and LA,, with each of which 1s associated vertical antennae, R, and

R respectively. While the characteristic of a loop antenna, as shown in Fig. 5, is such as to receive equally well in opposite directions, such loop antenna may be made fairly uni-directive by associating therewith a ver-' tical antenna. Thus, for example, the receiving structure X would be adapted to receive 'efii'ciently from the west whereas the structure X would be adaptedto receive efficiently from the east by the, proper phasing of the currents set up in the vertical and the 'loopantennae; The output side of the loop antenna LA is connected with a demodulator M with which is also connected an oscillator 0 adapted preferably to generate oscillations of the carrier frequency f,. The output side of the modulator M is connected with a low pass filter F which in turn is connected with an arnmodulator M plifier A and the output side of the latter is connected to the modulator M with which the oscillator 0 is also connected.

loop antenna LA is connected with a trans lating circuit, including the demodulator M low pass filter F amplifier A and p The oscillator 0 is connected with the demodulator M and the demodulator M The output side of each 'In similar manner, the output side of the of the modulators is connected with a common output circuit L wh ch in turn is connected to the antenna T through a circuit containing a band'filter F and an ampli- The mode of operation of the circuit shown in Fig. a is, in general, similar to that shown in Fig. 2. Oscillations arriving at the repeater RR, from the west, that is, from station A,'would, of course, be imthat is, the, signal current a, will pass through the filter F and, when amplified by A will be impressed upon the modulator M together with oscillations of the carrier frequency f,.- The resultant bands f +s and f 's will pass to thecommon output circuit L but since the filter F is adapted to transmit only the lower side band, that is,.f s, current at that frequency will pass therethrough and when amplified byA will be radiated by the antenna T This antenna has no directive qualities so that energy therefrom would be radiated in substantially all directions. However, since the frequency of the radiated oscillations is different from that for which the loop antenna circuits are tuned. (by virtue of their inductance and the capacity of the condensers K and K substantially noneof this energy will be absorbed by these antennae and accordingly local singing at a repeater point is avoided.

In like manner, oscillations of the frequency f arriving at repeater RR, from the east will be mainly absorbed by the antenna X since this antenna is selective of oscillations from the east, and the resultant current will be translated in. frequency by the translating circuit consisting of the demodulator M .the filter F the amplifier A and the modulator M together with the local source of carrier frequency O The re sultant bands of frequencies will be impressed upon the filter F which, as hereto fore stated, will transmit only the lower side band, viz, f Oscillations of this frequency would therefore be radiatedby the antenna T 'in substantially all directions but interference would be prevented in a manner similar to that herein set forth.

If it were desired to control the direction of the transmitted oscillations from the repeater shown in Fig. 4, the outputside of the modulators M and M (along the line a, a) may be connected withthe common trunk circuits L and L of F ig- 2,'by connecting that part of the circuit to the left of the line a, aof Fig. 4, with that part of the circuit of Fig. 2 to the right ofthe line Z), Z). In such a modificationof Fig. 4, the results of modulation of M would be impressed upon the filter F ofFig. 2, and the current of the frequency passed by this filter would be amplified :by A and impressed upon the common trunk L 1 The resultant oscillations would be radiated by the antennae T T etc.,' ina given direction, depending upon the phase adjustment of the odd numbered phase shifters, PS -PS etc., and in like manner, the products of modulation of M of Fig. 4 would be selected and amplified and radiated in a definite direction, depending upon. the adjustment of the even numbered phase shifting devices connected between. the transmitting antennae and the common trunk L It will be seen that the arrangement shown in Fig. 4: reduces the frequencies required for transmission between the stations A and B. of Fig. 3 to two, irrespective of the number of intervening repeater stations. Furthermore, in the arrangement shown in Fig.4, reception from both directions is effected at the same frequency and transmission'in both directionsis also efiected at the same frequency, which frequency is widely different from the reception frequency to prevent local singing at'the repeater station. While this invention has been described as embodied in a particular form and arrangement of parts, it is to 'be understood that it iscapable of embodiment, in other and different forms within the spirit and scope of the appended claims.

What is claimed is:

1. .In'a radio repeating, system having,

terminal stations and a plurality of repeater stations located there between in which simultaneous two-way signaling is effected by using for each transmission channel a transmitting wave of different frequency from the received wave, the method for limiting throughout the system the number of frequencies necessary for the transmission of each signaling channel to those transmitted and received by any terminal station, which consists in selecting the frequencies of the waves simultaneously transmitted from both terminal stations so that at any repeater station the oppositely traveling waves received thereby will be of the said waves.

taneous two-way signaling is efiected by requency and controlling :the direction of radiation of each of sai.dwavesl 1 same frequency, changing at eachrepeater station the frequency of both of the said waves by the same amount and radiating both of said waves at the same frequency without producing interference between the '2. In a radio repeating system having station's'located therebetw'een in which simulusing for each transmission channel transmitting wave of diflerentfrequency from the received wave, themethod for limiting throughout the system the'frequencies necessary for the transmission ofeachsignaling channel to those transmitted and received by any terminal station, which consists in selecting the frequencies of the waves simultaneously transmitted from both terminal stations so that at any repeater station'the oppositely traveling waves received thereby will embrace the same band of frequencies,

changing at each repeater station the frequencies of each of said bands by substan tially the same amount and radiating bands embracing substantially the. same frequencies without producinginterference between. the said bands. I g

3. In a radio repeating system having terminal 'stationsand a plurality of re peater' stations located therebetween in which two-way signaling is effected by using at each terminal station a' transmitting wave of different frequency from the receiving wave, the method for limiting throughout the. system :the' frequencies to those transmitted and received by. any terminal station, which consists in selectively receiving'at each of said repeater stations east and west waves of substantially the same frequency, changing the frequency. of the said waves by the same amount, radiating both of said waves at substantially. the same 4. 111 a radio repeating, system having terminal stations and a plurality. of repeater stations located-therebetween in which-twoway signaling is effected by using at each I terminal station a transmitting wave of different frequency from the receiving wave, the method for limitingthroughout the system the frequencies to those transmitted and received by any terminal station, which consists in selectively receiving at each of said repeater stations east and west waves em bracing substantially the same band of frequencies, changing the frequencies of both waves by the same amount, radiating both of said waves and controlling the direction of radiation of each of said waves.

. 5'. In a radio repeating system having terminal stations and an even number of repeater stations located therebetween, the method of relaying a two-way signaling channel between said terminals output sidesof any repeater station or between the stations themselves, which consists in modulating at each station a carrier frequency f by a signaling frequency sl, selecting and transmitting from oneterm1- nal station the f-l-s component of modulation, selecting and transmitting from the other station the f-s" component, whereby both waves received at any repeater station will be of the same frequency, changing the frequency of both waves at each repeater stationby the frequency 28 and radiating both of said waves from each repeater station at the same frequency.

6. In a radio repeating system having terminal stations and'an even, number of repeater stations located 'therebetween, the method of relaying a two-way signaling channel between said terminals without producing interference between the input and output sides of any repeater station or between the stations themselves, which consists in modulating at each station a carrier frequency f by a band of signaling frequency s, selecting and transmitting from one terminal that band representing the f|s-l component of modulation, selecting and transmitting from the other station that band representing the f-s component, whereby both waves received at' any repeater station will embrace the same band of frequencies, changing the frequencies of both waves at each repeater station by the frequency 28, thereby producing the side band opposite to that received at the said repeater station andradiating from the said repeater station both waves embracing the same band of frequencies.

7 In a radio repeating system having ter minalstations and an even number of repeater stations located therebetween, the

method of relaying a two-way signaling channel between saidterminals without producing interference between'the input and output sides of any repeater station orbetween the stations themselves, which consists in directively receiving at each repeater station oppositely traveling waves embracfrequency, of means for controllingthe directivity of reception of the said antennae,

a translating circuit having means ;assoelated therewlth to change'the frequency of all received waves by substantially the same amount, a plurality of transmitting an- 'tennae adapted to transmit the said waves at the frequency to whiclrthey have been changed, and means for controllingthe' direction of radiation of the said waves from the sald transmitting antennae.

9. In a radio repeating system, the com bination with a directionally controlled rIeceiving antenna system arranged to receive waves from different directions of the same frequency or the same band of frequencies, a frequency translating circuit arranged to change the frequency of allreceived waves by the same amount, and a directionally controlled transmitting antenna system-arranged to transmit each. of the'said waves of changed frequency in a predetermined direction. I

10. In a radio repeating system, the combination with a directionallycontrolled receiving antenna system arranged to receive from different directions waves having the same frequency or band of frequencies, a frequency translating circuit having means to change the frequency of each of the received waves by the same amount, and a directionally controlled transmitting antenna system having means totransmit the said waves of changed frequency in different predetermined directions.

In testimony whereof I have signed my name to this specificationthisl5th day of 

